The invention is based on a circuit arrangement according to the preamble of the main claim. Electrostatic filters are known which are used in industrial plants for separating dust particles from exhaust gases. These electrostatic filters are connected to high-voltage supplies whose voltage is regulated. The output voltage is fed to a regulator which controls the high voltage. A suitable high voltage can be produced in a simple manner for the electrostatic filters used in industrial plants by means of the available mains voltage. For an application in motor vehicles, where there is only a d.c. voltage of 12 volts, for example, as vehicle voltage, the known circuit arrangements are not suitable for the high-voltage supply of soot filters. The electrostatic filter is operated in the motor vehicle in sharply diverging areas. Throughput, composition, soot charging, moisture and temperature of the exhaust gas vary considerably within the entire speed and load ranges of the motor and change abruptly in intermittent operation of the motor. The impedance of the discharge and the breakdown limit of the discharge depend heavily on these parameters and fluctuate accordingly. The current which is fed into the filter and/or the operating voltage must be correspondingly adjusted to predetermined values in order to ensure a proper functioning of the filter in the entire motor operating range. It must be taken into consideration that the electrostatic filters in motor vehicles must be operated particularly intermittently and with throughput fluctuations of a factor of 10, whereas the known filters in large-scale plants are operated substantially steadily with a fixed operating point.